Novel surgical approach to neoplastic lesions in the distal part of the urethra: A pilot cadaver study comparing open and hybrid techniques

Abstract Tumours of the distal urethra in female dogs are often difficult to treat, and the surgical methods described thus far have technical limitations. This study aimed to present a novel approach to the surgical treatment of distal urethral tumours. This study used dog cadavers to evaluate the technical feasibility of surgically removing neoplastic lesions in the distal urethra and compared surgical outcomes of open surgery with those of hybrid surgery (combination of laparoscopy and open surgery). Open intact, open spayed, hybrid intact, and hybrid spayed dog cadaver groups underwent surgery (n = 6 per group). The novel surgical method was based on vulvovaginectomy (ovariohysterectomy in intact dogs), resection of the distal part of the urethra, and pre‐pubic urethrostomy. Outcomes of interest included technical feasibility of each procedure, using both surgical techniques, wound length, time required to complete the procedure, and the incidence of intraoperative ureter and rectum injuries. Surgical technique and reproductive status affected operating time. Technique choice affected wound length; the surgical wound was longer in the open group than in the hybrid group. Macroscopic evaluation of the rectum did not reveal any damage to the wall. There was no evidence of ureter leakage or obstruction in any case. The present findings suggest that both open and hybrid surgery can be used to treat distal urethral tumours.

management. 4,5 The technical possibilities of vaginourethroplasty are limited, 4,5 while pre-pubic urethrostomy alone is a palliative form of treatment. Other palliative approaches include cystostomy, 6,7 urethral stenting [8][9][10] and transurethral resection. 11 The present study aimed to propose a novel surgical technique for the treatment of proliferative changes in the distal part of the urethra in cases that require an oncological margin. This study aimed to The duration of each procedure was measured, and the ureter and rectal wall were examined postoperatively for evidence of damage.

| Open surgery
Median laparotomy involved a cutaneous incision made from the umbilical region (open intact group) or from a half-way point between the umbilicus and pubic symphysis (open spayed group) up to the perineum, surrounding the vulva with an elliptical incision ( Figure 1A).
The pelvic bone osteotomy was performed according to the technique described by Allen and Crowell. 12 The space between the right and left adductor muscles was cut and the adductor muscles were elevated subperiosteally from the pubis and ischium to expose the obturator nerves and approximately half of the obturator foramina. The pre-pubic tendon was transected along the left side of the pubis to the proposed pubic osteotomy site. Holes were drilled in the pubis and ischium on both sides of the four proposed osteotomy sites and craniocaudally along the left pubis. The pubic and ischial osteotomies were performed using an oscillating saw (Conmed, Conmed Corporation, NY, USA). The internal obturator muscle was elevated subperiosteally from the left pubis and ischium, allowing retraction of the central bony plate to the right. After obtaining access to the pelvic cavity, the main part of the procedure was performed ( Figure 1B     The first trocar for laparoscopic optics was inserted using the Hasson method at the level of the umbilicus. 13 After insufflation of the abdominal cavity (CO 2 pressure of 8 mmHg), two consecutive trocars were inserted caudal-laterally to the first optical trocar ( Figure 2D) under the control of the endoscope.

| Hybrid surgery
In the hybrid intact group, the procedure started with the removal of the right ovary and dissection of the same-side broad ligament using a vessel-sealing device (BiCision ® , Erbe, Tübingen, Germany).
An optical trocar was temporarily used opposite to the operated side of the working trocar to facilitate visualization during ovarian removal and dissection of the broad ligament of the uterus ( Figure 2E). After completing these procedures on both sides, the uterine body was dissected up to half of the urethral length. The vesicogenital and pubovesical pouches were opened and dissected bluntly using laparoscopic forceps. The fatty tissue surrounding the urethra, uterine body and vagina was dissected and severed ( Figure 3A,B).
In the hybrid-spayed group, the procedure started with the dissection of the uterine stump to the same level as that in the hybrid intact group ( Figure 3C). The remaining procedures were identical in

| Surgical time and length of postoperative wounds
The duration of surgery in all groups was measured from the first skin incision to the last skin suture. The postoperative wound length was measured after the surgical procedure was completed, and the continuity of the rectal wall was assessed before the ureter leakage was tested. The length of the wound in the open technique group was measured using a standard tape measure, while that in the hybrid technique group was measured as the sum of the wound length at the level of the removed vulva and trocar wounds. The lengths of the post-urethrostomy wounds were not measured, as they were similar in all groups.

| Postoperative complications
All ureters were post-surgically tested for leaks. After the procedure was completed, the abdominal cavity was reopened (right paramedian access), and the ureters were severed at the level of the kidney. The appearance of the rectum was also assessed macroscopically for any evidence of damage.  All surgical procedures were feasible, independently of dog breed or cadaver weight. No case of leakage or obstruction was observed.

| Statistical analyses
There was no damage to the rectum wall.

| DISCUSSION
Neoplastic lesions of the urinary system account for <2% of all tumours observed in dogs, and their treatment remains a challenge. 1,2 Approach to lesions located in the distal part of the urethra, where organs are surrounded by pelvic bones is particularly challenging, and previously described methods have some limitations. [4][5][6]8,15 Consequently, in the present study, we aimed to develop a novel surgical method applicable in this context and to test it on cadavers.
Indications for urethrostomy in companion animals include extensive injuries and neoplastic lesions of the distal urinary tract. 15,16 Feasible urethrostomy sites in female dogs include the abdominal wall, 15 perineum, 14 and vagina. 15,16 Suturing the urethra in a way that creates tissue tension can lead to postoperative complications. 14,15 Therefore, in cases of urethra length insufficient for perineal urethrostomy, prepubic urethrostomy is recommended. 17 In the present study, we sutured the urethra at the midline in the hybrid group because an extensive surgical wound was not present at this site; similar findings were observed in the classically operated group, affecting the performance of the urethrostomy lateral to the laparotomy line. Such urethrostomy sites are commonly used in companion animal surgery. 15 Midline pre-pubic urethrostomy is associated with a lower risk of urine leak onto the limb during voiding; therefore, some surgeons prefer to suture it to the midline laparotomy wound. In the group undergoing hybrid surgery, the authors performed urethrostomy with the assistance of laparoscopy, which allows the urethra to be sutured in a more favourable position. Queiroga et al. 18 performed an experimental pre-pubic urethrostomy assisted by laparoscopy in rabbits. A similar surgical procedure was described in a cat undergoing surgery due to recurrent feline lower urinary tract disease. 19 In the present hybrid group, the urethra was prepared laparoscopically. This (B) (A) (C) F I G U R E 5 (A) Catheterization of the ureter at the level of the kidney was used to assess the patency and tightness of the ureters. (B) Presence of ink at the site of the urethrostomy suggests ureter is patent (blue arrow). (C) Ureteral patency and tightness were assessed using coloured ink filling (green arrow) procedure may help ensure radical removal of the distal part of the urethra and reproductive organs under visual control. This approach may be used in cases of neoplastic tumours of the distal part of the urethra that require extensive resection, allowing healthy tissue margin to be preserved.
The lowest risk of postoperative urinary incontinence has been reported for the urethra resected between one-third to half of its length measured from its distal part in humans 20 and animals. 5,14 Using these indicators, White et al. 5  Ureteral injuries are serious complications that may occur in this context. [27][28][29][30] No case of ureteral wall damage was observed in the present study; however, particular care should be taken to prevent this type of damage in living animals undergoing surgery. Ovariohysterectomy is among the most common procedures performed on companion animals. [31][32][33][34] Several relevant laparoscopic techniques have been described, 24,32,35 including insertion of an optical trocar into the linea alba at the umbilicus level and that of two working trocars lateral to the optical trocar, 35  This study has some limitations. First, the present study involved dog cadavers, precluding meaningful discussion about intraoperative difficulties associated with operating on live dogs. Second, the use of cadavers in this study removed the opportunity for short-and longterm follow-up assessments. Third, all study procedures were performed on unchanged urogenital organs; consequently, it remains unclear whether a healthy tissue margin can be maintained during the removal of neoplastic lesions in all cases. Nevertheless, this was a pilot study whose aim was to evaluate the feasibility of the proposed technique; this study has achieved its aim.

| CONCLUSION
The proposed open and hybrid methods for the surgical treatment of urethral tumours are technically feasible. These procedures may be considered in animals ineligible for other less extensive procedures.
In vivo experimental studies are required before the proposed techniques may enter veterinary practice.